This invention relates to cleaning material from a support surface, and more particularly, it relates to an apparatus and method for removing liquid developer from a photoconductive or other surface.
In the development of electrostatic latent images where liquid developers are used to develop the image on the reusable photoconductor surface or on a reusable interposition surface, liquid developer remains on the surface after the developer image is transferred to a substrate. In these processes and apparatuses where the surface is reused to develop subsequent images, the residual liquid developer must be removed therefrom to such an extent that the residual developer will not interfere with subsequent imaging causing image or non-image patterns and smudges of developer which transfer to subsequent substrates. Cleaning blades are commonly used to remove the residual liquid developers from these and other support surfaces.
U.S. Pat. No. 3,660,863 issued to Gerbasi on May 9, 1972, discloses a scraper blade acting on a xerographic drum for removing particulate toner material from the drum. In Gerbasi, the cutting edge of the blade, that is, the edge of the blade formed by the upper face surface or top surface and the front side surface, is positioned slightly below the horizontal center line of the drum and the cutting edge held in a manner to readily cut or chisel the particulate toner material from the drum surface. This configuration works fine for particulate toner material, however, when used with liquid developers this configuration causes fluids to permeate machine parts when they drip from the support surface in various spots. Blade cleaning is also described by Royka et al. in U.S. Pat. No. 3,552,850 wherein at least one self-adjusting flexible cleaning blade for pressure contact cleaning of the imaging surface is shown. In Royka et al, the leading edge of at least one cleaning blade is preferably positioned to form an acute angle of less than about 90.degree. and greater than about 20.degree. with the confronting portion of the imaging surface or plane tangent to the imaging surface at the line of blade contact to clean particulate toner from photoconductive members when means to supply a dry solid lubricant to the imaging surface are provided. As discussed above, this cleaning technique is operable for particulate toner, but when liquid developers are used, the fluids collect on the photoconductive members and fall into machine parts in various locations of the copier. Furthermore, the wiping action does not suitably remove the liquid developers from the surface.
In accordance with the present invention cleaning blades may be designated as scraper blades or wiper blades. A scraper blade is defined as one wherein the stem extends towards the top in the upstream direction of the drum's movement and when pressed against the drum exerts a chiselling action on the material on the drum surface. When such a blade is used for cleaning liquid material from a support surface which in operation moves uphill, problems are encountered in disposing of the liquid cleaned or removed from the surface. It may run back over the uncleaned part of the surface and drip off at random positions.
A blade which in operation is pressed against a support surface so that it is bent along its length in the downstream direction of the drum motion has a wiping action as it tends to be lifted up by material moving with the drum surface, but will wipe any material moving in the opposite direction away from the drum surface. A wiper blade is defined in accordance with the present invention as one in which the stem extends in the downstream direction of the drum motion. As used herein, upstream and downstream refer to drum motion.